Youth thin armed sunglasses?

Just curious if anyone has found any thin armed sunglasses for kids that'll easily fit inside a full face helmet. My son is 6.5 years old and rides with me now and then but the helmet we have for him no longer has any tinted visors available. The sunglasses he has now have either too thick arms or they bend in and get pressed into his skull. I'm hoping to find something with basically a metal strip for an arm that'll slide into a helmet that doesn't have glasses slots built in.